1. Field of the Invention
The present invention relates to a method for manufacturing a ferrite magnet device, a method for manufacturing a non-reciprocal circuit device including the ferrite magnet device, and a method for manufacturing a composite electronic component including the non-reciprocal circuit device.
2. Description of the Related Art
Conventional non-reciprocal circuit devices, e.g., isolators and circulators, have a characteristic that signals are transmitted in a specific direction and are not transmitted in the reverse direction. For example, an isolator is used to transmit circuit portions of mobile communication equipment, e.g., automobile telephones and cellular phones, by utilizing this characteristic.
In general, this type of non-reciprocal circuit device includes a ferrite magnet device composed of a ferrite body provided with a center electrode and a permanent magnet arranged to apply a direct current magnetic field thereto and a predetermined matching circuit device including a resistance and a capacitor. Furthermore, a composite electronic component including a plurality of non-reciprocal circuit devices, or a composite electronic component including a non-reciprocal circuit device and a power amplifier device have been provided as modules.
In the above-described non-reciprocal circuit device and composite electronic component, electrical characteristics thereof must be measured and adjusted. Japanese Unexamined Patent Application Publication No. 2002-299914 discloses that the capacitance and the resistance are measured so as to have a predetermined capacitance value and resistance value or they are adjusted to predetermined values by trimming or other suitable methods before being connected to the center electrode, and the center electrode is subjected to a magnetic force adjustment after being assembled into a non-reciprocal circuit device. Japanese Unexamined Patent Application Publication No. 2005-117500 discloses that a non-reciprocal circuit device and a power amplifier are assembled into one unit and, thereafter, the magnetic flux density of a permanent magnet is adjusted.
However, in a non-reciprocal circuit device or the composite circuit device including the non-reciprocal circuit device, there are large fluctuations in characteristics due to variations in characteristics of the ferrite body provided with the center electrode or the permanent magnet, and in particular, variations in magnetic force of the permanent magnet. Consequently, the inductance of the center electrode deviates significantly from a predetermined value because of this factor, and non-adjustable devices may result. In the manufacturing method according to the related art, the magnetic force is adjusted at a stage in which the matching circuit device has been incorporated or the power amplifier has been combined. Therefore, if a non-adjustable device is found, the non-adjustable device has to be discarded, and there is a problem in that the matching circuit devices, power amplifiers, and other combined components are wasted.